Internal/External Hardware Flashcards
Barcode Reader Principle of Operations
1) A light is shone at a barcode
2) The Light is reflected back, black bands reflect less light, white bands reflect more light
3) Light Sensor measures the amount of light reflected
4) The light reflected is converted into an electrical signal - this is analysed to determine the value encoded in the barcode
5) Data transmitted as binary codes to the computer, often sent as ASCII codes
Laser Printer Principle of Operations
1) The drum inside the printer is coated in a negative charge
2) A Laser Beam is shot at the drum, which removes any electric charge on the drum where the image should be black
3) The toner is given a positive charge, which means it is attracted to the drum, so the drum picks it up
4) Colour Printers have 4 different toner mechanisms
5) Paper is rolled over the drum to transfer the toner
6) The toner is heat treated to fuse the toner onto the paper
Digital Camera Principle of Operations
1) The shutter opens and lets light in through the lens
2) The light is focused onto a censor (CCD)
3) The sensor uses transistors to generate a binary value
4) As the light hits the sensor it is converted into electrons, the amount of charge is recorded in binary form - an ADC is used to convert this
5) To record colour, three different filters are used: Red, Green, Blue
6) Data is stored on removable storage devices (flash memory)
7) Typically stored in compressed files (e.g. PNG)
RFID Principle of Operations
1) When an RFID tag is scanned, the reader emits radio waves which are picked up by the tag’s antenna
2) The power induced in the tag’s antenna from these waves powers the chip, which uses the antenna to emit its own radio wave which contains the information held in the chip
3) The wave is picked up by the reader which decodes the information and returns to the computer
What are the uses of RFID?
Tagging Pets/Livestock, Debit Cards, Hotel Room Keys
